1. Field of the Disclosure
The present disclosure relates broadly to a finisher transport module system, and more particularly, to an improved rotator and translator mechanism for use in controlling the orientation and alignment of sheets passing through a finisher transport module.
2. Description of Related Art
Finishing transport module systems for rotating and translating sheets passing through the system are known, for example, U.S. Pat. No. 6,811,152 which is incorporated herein by reference along with the references cited therein. Another example is shown in prior art FIG. 1, where a sheet rotator and translator mechanism for a finishing transport module 10 includes two rotator disc motors 30 and 32 that drive each rotator disc 12 and 14 independently. When turning in the same direction and at the same speed, the sheet will pass through the rotator device like any normal nip set (no rotation or directional offset). With the motors still rotating in the same direction and speed, steering idlers 16 and 18 can be rotated around the periphery of the discs to alter the inboard/outboard position of a sheet without rotation. This is useful for offsetting sheet sets in a stacker or for changing center and edge registration for finishing devices located downstream. To know when the sheet has been offset the desired amount, there is an edge sensor 40 that is positionable by a lead screw. The lead screw motor 33 positions the sensor 40 a set distance inboard/outboard for one sheet set, then repositions the sensor to detect the inboard/outboard position for the next sheet set. For sheet rotation, the motors controlling the rotator discs simply spin at different velocities. The larger the velocity differential, the faster the media is rotated.
A problem with this design is that the discs spin horizontally while the idlers spin vertically. Therefore, if the idler were to ride along a wide nip (like normal nip sets) there would be a relative motion issue. Prior art FIG. 2 illustrates a top view of a wide disc nip design that includes a disc 45 that forms a nip with idler 46. It can be seen that with R1 being far smaller than R2 there would be a significant relative motion problem. This would result in heavy marking, slip, unreliable rotation and translation, etc. To fix this, a very thin, high-pressure nip is used. The high pressure nip is shown in prior art FIG. 1 and includes a very small contact point or ridge 13 between disc 12 and the idler 18 and 15 between disc 14 and idler 16. This effectively removes the relative motion since there is essentially only one radius, but the pressure is very high. This high pressure is necessary to prevent slip, but ultimately does cause marking on certain media, especially coated sheets.
Thus, there is a need for a solution to the problem of the tendency of existing finishing transport module systems to mark certain types of coated media.